

A193109


Least k such that 2^x + k produces primes for x=1..n and composite for x=n+1.


0



0, 1, 9, 3, 225, 15, 65835, 1605, 19425, 2397347205, 153535525935
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OFFSET

1,3


COMMENTS

All terms except the first four are congruent to 15 mod 30.
a(10) was found in 2005 by T. D. Noe and a(11) was found in the same year by Don Reble.
Other known values: a(13)=29503289812425.


LINKS

Table of n, a(n) for n=1..11.


MATHEMATICA

Table[k = 0; While[i = 1; While[i <= n && PrimeQ[2^i + k], i++]; i <= n  PrimeQ[2^i + k], k++]; k, {n, 9}] (* T. D. Noe, Jul 21 2011 *)


CROSSREFS

Another version of A110096.
Cf. A092506, A057733, A104070, A144487, A008597.
Sequence in context: A195312 A038293 A119516 * A242069 A197828 A116393
Adjacent sequences: A193106 A193107 A193108 * A193110 A193111 A193112


KEYWORD

more,nonn


AUTHOR

Arkadiusz Wesolowski, Jul 21 2011


STATUS

approved



